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Brown Adipose Tissue: An Opponent of Obesity

With the rise in obesity over the last few decades, scientists have grown interested in studying this condition and the illnesses that come with it – type 2 diabetes, heart disease, hypertension, and various types of cancer are directly linked to obesity.

For one researcher, brown adipose tissue and its connection with obesity was intriguing. Dr. Aaron Cypess of the Joslin Diabetes Center published a paper in The New England Journal of Medicine with his colleagues on the associations between this tissue and obesity.

Essentially, obesity occurs from the imbalance of energy expenditure and energy intake. Rodents such as mice or rats use brown adipose tissue to assist in regulating energy expenditure. Human infants also use a similar system through thermogenesis, which is a method for heat production in warm-blooded mammals and some other thermogenic organisms.

While infants use brown adipose tissue for energy regulation, adult humans have been long considered to have no physiological application for this tissue type. Cypess and his colleagues looked at more than 3,000 CT and PET scans of nearly 2,000 patients to analyze the accumulation of brown adipose tissue.

Collections of this tissue were identified as more than 4 millimeters in diameter and illustrated high metabolic activity by absorbing at least 2.0 grams per milliliter of 18F-fluorodeoxyglucose. The researchers performed immunostaining on biopsied tissues extracted from the neck and clavicle regions of patients post-surgery.

The results of this research show that a large amount of brown adipose tissue was located in the area stretching from the anterior neck to the thorax. Scans determined the type of tissue in this region. More than twice as many women versus men exhibited positive scans indicating brown adipose tissue. Women also had a larger mass of this tissue and greater uptake of 18F-fluorodeoxyglucose.

The detection of brown adipose tissue was also inversely correlated to a person’s age, body-mass index among older subjects, and beta-blocker adoption. The most important finding of this research is that the quantity of brown adipose tissue is inversely related with body-mass index. This is especially true in older individuals and may indicate a potential role of this tissue in adult human metabolism.

One paper published in Nature Medicine by Matthew Harms and Patrick Seale from the Perelman School of Medicine explains that brown fat cells are able to lower the risk of metabolic disease including obesity in mouse models and is associated with thinness in humans.

The two scientists studied the development and proliferation of brown and beige adipocytes in mice. The researchers were able to show how certain secretions of the adipose tissue are able to draft brown and beige fat cells. In mice and other rodents, various tissues are able to secrete these particular factors. The particular tissues are part of the liver, muscles, blood vessels, thyroid, and even the cardiovascular system.